Officially called Multi-Path TCP the new technique enables an iPhone or iPad with Wi-Fi and 3G/4G to use both Wi-Fi and Cellular data at the same time, and switch seamlessly between the two. For a device that is permanently connected to the Internet via Wi-Fi and 3G/4G the new technology could have profound effects on performance. To start with its been quietly rolled out to just Siri, but we expect Apple to widen access to further iOS apps and the operating system as a whole.

Christopher Mims from Quartz explains just why it’s so important: “This is the first time that this new means of connecting to the internet has appeared in a commercial product. That it showed up in Apple’s software and not Google’s shows that Apple’s technical chops are substantial, even when the company isn’t highlighting what it’s up to.”

Making the iPhone connection more reliable

Anybody who has used an iPhone in an area with poor Wi-Fi will know what happens when they walk away from the base station. There is a point where the iPhone remains connected to the Wi-Fi connection, but can’t get a signal. Multi-Path TCP solves this problem because data from an app is being sourced by both Wi-Fi and the mobile data connection.

There’s more though. At the moment if a iPhone user’s connection to either Wi-Fi or 4G drops out (as they move around) then the data is dropped with it. Whatever you were trying to access: a web page, email, or Siri conversation is lost. But under Multi-Path TCP the device can seamlessly switch from one data source to another, to carry on providing the same data packet. This is important on a mobile device like an iPhone or iPad, than on a laptop or desktop because these devices move around more.

That Apple has implemented this technology first in any consumer electronic device, and that device was a phone highlights just how much the internet has changed since TCP was first envisioned. It is primarily accessed on mobile devices that are quickly moving in physical location.

While the average iPhone consumer can’t be expected to know much about TCP (Transmission Control Protocol) and IP (Internet Protocol) the effect on day-to-day usage could be profound. To start with Siri should be much faster and more reliable than before, and you should get far fewer “I’m sorry” messages from Siri. Moving forward a device that is consistently reliable at delivering web pages, email and other services is simply much more fun to use. The user simply notices that the iPhone is more reliable than it used to be, or than phones from other people.

Apple has secured the Internet’s future

Apple’s implementation of Multi-Path TCP in the iPhone has pretty much secured the new format’s future. Mims argues that it’s “the first and most important change to the low-level architecture of the internet to reflect the fact that our connections to it are more mobile and wireless than ever.”

On the technical level it has a more profound change than simply making Siri and other services more reliable. It shifts control from the transmission protocol from remote hosts to local devices, in effect enabling the devices themselves to determine how data is shifted.

What is TCP and how does Multi-Path TCP work

As a quick refresher in the Internet: data (email messages, web pages, and so on) is broken up into small 8-bit packets (called octets) using Internet Protocol (IP). You know this because your computer has an IP address: where these data octets are sent from, and delivered to.

These octets fly out of your computer and hopefully land in another computer somewhere else. The bit in the middle where they whiz around in the world is handled by TCP (Transmission Control Protocol). Because the octets are split up they can go via different routes, different servers, and arrive at different times. TCP ensures they arrive at the same place and are assembled in the right order.

That’s how the Internet works. Although the “series of tubes” metaphor is funnier.

The thing with TCP is that it’s only really designed to handle and recognise certain packets of data. If the network is unpredictable then packets can be lost, or duplicated or delivered out of order.

What is Multi-Path TCP

Multi-Path TCP transfers control of TCP from the network operator to the devices themselves. So it becomes more of an end-to-end solution. (You send something to someone else and sort out the details between the two devices).

Computer scientist Mark Smith suggested in this Ausnog presentation that Apple’s implementation of Multi-Path TCP represents a larger change in how the internet is built, one in which individual devices decide how to communicate rather than relying on the systems already in place. This could allow for whole new types of computer communication, and a whole different type of Internet.